a201-11f-23-WorldFullOfPlioPleistoceneHominins -...

Introduction to Biological Anthropology: Notes 23 A world full of Plio-pleistocene hominins  Copyright Bruce Owen 2011 -Let’s look at the next chunk of time: 3.0 – 1.0 mya -often called the Plio-pleistocene (end of the Pliocene, beginning of the Pleistocene) -numerous species of bipedal apes (hominins), more varied adaptations -in some times and places, 2 or 3 hominins lived in the same environment at the same time -Australopithecus species -presumably descendents of the earlier A. afarensis and maybe others -at least 5 species during this period -up to 2, probably 3 at the same time -called australopithecines in general -Paranthropus species -at least 3 species during this period -up to 2 at the same time -called paranthropines in general -plus possible descendents of Kenyanthropus , although no fossils have been found yet -plus, halfway through this period (1.8 mya), the first species of our genus: Homo-we’ll look at those later -All the Plio-pleistocene hominins (3.0 to 1.0 mya) shared certain basic features: -all bipedal -all had similar small bodies, only slightly larger than Lucy ( A. afarensis ) -all had chimp-size brains (chimps have a cranial capacity of about 300-400 cc; gorillas 540 cc) -except one late australopithecine ( A. rudolfensis ) that evolved a larger brain -Plio-pleistocene australopithecines (3.0 to 1.0 mya) -one type of hominin, of two or maybe more general types -australopithecines all shared a peculiar heavy back-teeth grinding adaptation, probably for hard seeds like grasses -large molars (and premolars) -reduced canines -zygomatic arches leave space for large temporal muscles -zygomatic arches are sturdy for attaching strong masseter muscles -fairly prognathic face -probably several different lineages -all went extinct, unless one led to humans -Some examples of australopithecines: -Australopithecus africanus (3.0-2.2 mya)-both South Africa and East Africa -enough fossils known that we can say a bit more about this species than others, such as: -still have marked sexual dimorphism in body size -even though their canines are reduced, probably to facilitate grinding

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Intro to Biological Anthro F 2011 / Owen: World full of Plio-pleistocene hominins p. 2 -this means that males no longer had much larger canines than females -but the body size difference suggests that there was still lots of male-male competition, so they were not monogamous -growth rings in tooth enamel suggest… -short, rapid juvenile development -similar to chimps, not humans -suggests that behavioral complexity and learning were more like chimps than like humans

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